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    SubjectRe: finding out the value of HZ from userspace
    On Tue, Mar 23, 2004 at 10:04:22AM +1100, Peter Williams wrote:
    > Micha Feigin wrote:
    > >On Sat, Mar 20, 2004 at 12:28:00PM +0100, Stefan Smietanowski wrote:
    > >
    > >>>>>there is one. Nothing uses it
    > >>>>>(sysconf() provides this info)
    > >>>>
    > >>>>Seems to me that it would be fairly trivial to modify those programs
    > >>>>(that should use this mechanism but don't) to use it? So why should
    > >>>>they be allowed to dictate kernel behaviour?
    > >>>
    > >>>
    > >>>quality of implementation; for example shell scripts that want to do
    > >>>echo 500 > /proc/sys/foo/bar/something_in_HZ
    > >>>...
    > >>>or /etc/sysctl.conf or ...
    > >>>
    > >>
    > >>Then write a simple program already. How hard is it to write a program
    > >>that does a sysconf() and returns (as ascii of course) just the
    > >>value of HZ? Then do some trivial calculation off of that.
    > >>
    > >>HZ=$(gethz)
    > >>
    > >>If your 500 was 5 seconds, do
    > >>
    > >>TIME=$[HZ*5]
    > >>echo $TIME > /proc/sys/foo/bar/something_in_HZ
    > >>
    > >
    > >
    > >Will this be USER_HZ or kernel HZ?
    > >Someone earlier suggested it would be USER_HZ which would make it
    > >pointless.
    >
    > It has to be whatever enables user space to correctly interpret values
    > sent to user space as "ticks". That means USER_HZ and it's not useless
    > as it enables USER_HZ to be different and/or change without breaking
    > programs that use values expressed in "ticks".
    >

    Unless the kernel is converted to make that conversion possible then it
    is useless at the moment since userspace gets USER_HZ and the kernel
    proc interface speaks (KERNEL) HZ so userspace really has no idea how
    to speak to kernel space with 2.6.

    > >
    > >
    > >>I mean, come on.
    > >>
    > >>Then you include it in the default distro of choice so that
    > >>everybody can use it and there you are.
    > >>
    > >>If someone doesn't have "gethz" then they can download it.
    > >>
    > >>// Stefan
    > >>
    > >
    > >-
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    > >Please read the FAQ at http://www.tux.org/lkml/
    >
    >
    > --
    > Dr Peter Williams, Chief Scientist peterw@aurema.com
    > Aurema Pty Limited Tel:+61 2 9698 2322
    > PO Box 305, Strawberry Hills NSW 2012, Australia Fax:+61 2 9699 9174
    > 79 Myrtle Street, Chippendale NSW 2008, Australia http://www.aurema.com
    >
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